Ball will do this for many reasons. They are trying to get cooler than what the cool side can offer them, soaking to try and help a BM along, they ate arecently and are soaking to help support some of their body, mites, a shed in coming, they may be slightly dehydrated. There are many many reasons for a ball soaking some or just the nature of the animal some are health related. Best thing to do is just watch and see when you snake soaks keep notes: times, enviromental changes, did it feed, shed so on then you will know for sure.

Best of luck hope that helps